Unknown Fault with ABB-DCR600 DC Drive

HI,

Need an advice on fixing a ABB-DCR600 main control card SDCS-CON2A, the keyboard panel display indicates a "CON COMMUNIC FAULT ". The ABB manual defines this as a communication fault between SDCS-AMC-DC and SDCS-CON2A cards. Also, the seven segment display/LEDs of the SDCS-CON2A card indicates a power-up error E02 (RAM memory test error), and the red LED on the SDCS-AMC-DC is lighted. I already tried to de-energise and energise the drive and also replace the SDCS-POW-1C power supply board (from other unit) yet still the fault indication occurs.

Is there an explanation as to what caused these fault indication, How do I fix it?

Thanks...